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https://issues.apache.org/jira/browse/HADOOP-11387?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14252177#comment-14252177
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Jonathan Eagles commented on HADOOP-11387:
------------------------------------------
Posting warnings before the build artifacts are deleted.
{quote}
Multithreaded correctness Warnings
Code Warning
AT Sequence of calls to java.util.concurrent.ConcurrentHashMap may not be
atomic in org.apache.hadoop.net.NetUtils.canonicalizeHost(String)
AT_OPERATION_SEQUENCE_ON_CONCURRENT_ABSTRACTION: Sequence of calls to
concurrent abstraction may not be atomic
This code contains a sequence of calls to a concurrent abstraction (such as a
concurrent hash map). These calls will not be executed atomically.
{quote}
{quote}
Bug type AT_OPERATION_SEQUENCE_ON_CONCURRENT_ABSTRACTION (click for details)
In class org.apache.hadoop.net.NetUtils
In method org.apache.hadoop.net.NetUtils.canonicalizeHost(String)
Type java.util.concurrent.ConcurrentHashMap
Called method java.util.concurrent.ConcurrentHashMap.put(Object, Object)
At NetUtils.java:[line 291]
{quote}
> Simplify NetUtils#canonicalizeHost()
> ------------------------------------
>
> Key: HADOOP-11387
> URL: https://issues.apache.org/jira/browse/HADOOP-11387
> Project: Hadoop Common
> Issue Type: Bug
> Reporter: Haohui Mai
> Assignee: Li Lu
> Attachments: HADOOP-11387-121514-1.patch,
> HADOOP-11387-121514-2.patch, HADOOP-11387-121514.patch
>
>
> Currently {{NetUtils#canonicalizeHost}} uses a {{ConcurrentHashMap}} to cache
> the canonicalized hostname.
> {code}
> private static String canonicalizeHost(String host) {
> // check if the host has already been canonicalized
> String fqHost = canonicalizedHostCache.get(host);
> if (fqHost == null) {
> try {
> fqHost = SecurityUtil.getByName(host).getHostName();
> // slight race condition, but won't hurt
> canonicalizedHostCache.put(host, fqHost);
> } catch (UnknownHostException e) {
> fqHost = host;
> }
> }
> return fqHost;
> }
> {code}
> The code triggers a findbugs warning. The cache is used for caching NN
> resolution for the client-side {{FileSystem}} objects. In most of the use
> cases there are at most one or two instances in the cache. This jira proposes
> to eliminate the findbugs warnings and to simplify the code using
> {{CacheMap}}.
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